Introduction to Python Day 2

Verjinia Metodieva and Daniel Parthier

2025-02-04

Jupyter Notebook

Recap homework

Let’s take a look at the homework

Functions part 2

Goal of today

import numpy as np
import os

def AP_check(folder):
    AP_sweep_count = 0
    for filename in os.listdir(folder):
        if filename.endswith('.csv'):
            with open(os.path.join(folder, filename), 'r') as file:
                data = np.loadtxt(file, skiprows=1)
                if any(data > 20):
                    AP_sweep_count += 1
                    print("AP found in " + filename)
                else:
                    print('No AP in ' + filename)
    return AP_sweep_count

file_path = 'data/sweeps_csv/'
sweep_count = AP_check(file_path)
print(sweep_count)

Global vs. Local

Short interlude

  • Whole numbers: Integers int
type(1)
int
  • Real numbers: Floats float
type(1.0)
float
  • Most of the time it might not matter1
1 == 1.0
True
  • Sometimes there is a difference and we will see later why

Conditional statements

The important question of what to do “if” something happens.

  • Programming languages are languages
  • if something is True
    • you should do something
  • else
    • do something else
if statement:
    print("the statement is true")
else:
    print("the statement is false")

Multiple if-statements

value = 3
1if value == 1:
    print("the value is 2")
2elif value == 2:
    print("the value is 2")
3elif value == 3:
4    print("the value is 3")
else:
    print("the value is something else")
1
Check if value is 1
2
Check if value is 2
3
Check if value is 3
4
Execute block 
the value is 3

Short forms for conditionals

amplitude = 24
is_action_potential = "is AP" if amplitude > 0 else "no AP"
print(is_action_potential)
is AP
  • You can write a lot on one line
    • Do if you have to but be careful

How to check if everything is true?

  • Validate all of the statements in a list
everything_is_true = [True, True, True]
something_is_true = [True, False, False]

all(everything_is_true)
all(something_is_true)
True
False
  • Sometimes only something has to be true
any(everything_is_true)
any(something_is_true)
True
True

For loops

Enumerate

Range

List comprehension

Compare different functions

While loops

  • Perform a task while something is True
  • Be careful:
    • Some loops never finish (get stuck)
    • Make sure that condition for ending the loop can be fullfilled
while check_condition:
    perform_task()

Errors and how to read them

There are useful resources regarding errors

  • Simply googling works surprisingly well
  • You will often end up on stackoverflow
    • There is no question which was not already asked1

Types of errors

  1. SyntaxErrors
  2. NameError
  3. TypeError
  4. IndexError
  5. AttributeError
  6. etc.

Fix errors